In the options pits, overall volume has jumped to 1.8 times what's typically seen at this point in the day, with speculators split on the equity's near-term trajectory. Specifically, three of BIIB's top five options reside in the weekly 9/25 series, and buy-to-open activity has been detected at the 305-strike call, as well as the 295- and 300-strike puts.

Widening the sentiment scope reveals BIIB's options pits have been dominated by call buyers in recent weeks. At the International Securities Exchange (ISE), Chicago Board Options Exchange (CBOE), and NASDAQ OMX PHLX (PHLX), the security's 10-day call/put volume ratio of 1.54 ranks in the 75th percentile of its annual range, meaning calls have been bought to open over puts at a faster-than-usual clip.

Echoing this is the equity's Schaeffer's put/call open interest ratio (SOIR) of 0.92. Not only does this indicate call open interest outweighs put open interest among options expiring in three months or less, but it ranks lower than 87% of all similar readings taken in the past year. Simply stated, speculative traders are more call-heavy than usual toward BIIB.

Good news for those purchasing Biogen Inc's (NASDAQ:BIIB) near-term options: the stock's Schaeffer's Volatility Index (SVI) of 35% sits in the 30th percentile of its annual range. In other words, premium on the equity's short-term options is pricing in relatively low volatility expectations at the moment.